Heat exchanger having a plastic collecting tank

ABSTRACT

The invention relates to a heat exchanger, such as, for example, a liquid cooler, charge air cooler or the like, having two-part collecting tanks which are composed entirely of plastic and have inlet or outlet connecting pipes. One collecting tank part can have openings for receiving the ends of tubes, with the tube ends being adhesively connected therein, and with the two collecting tank parts being welded to one another at a weld seam which runs around the periphery of their walls. The two tank parts form an oval to round collecting tank cross section between the tubes, and the weld seam is situated in a seam preparation which is formed as a thickened portion of the walls of the tank parts. As a result of the invention, the heat exchanger is of particularly pressure-resistant design and is very production-friendly.

CROSS-REFERENCE TO RELATED APPLICATIONS

Priority is hereby claimed to German Patent Application No. DE 10 2007008536.4 filed Feb. 21, 2007, the entire contents of which isincorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates to a heat exchanger, such as, for example,a liquid cooler, having a two-part collecting tank which is composedentirely of plastic, with one collecting tank part having openings forreceiving the ends of tubes, with the tube ends being adhesively bondedtherein, and with the two collecting tank parts being welded to oneanother at a weld seam which runs around a periphery of their walls.

SUMMARY

DE 10 2006 002 627.6 and DE 10 2006 002 789.2 disclose conventional heatexchangers having two-part collecting tanks connected by means of awelding process, without going into any more detail as to how thecollecting tank parts must be configured for a welded connection and howthe welded connection and the production of the heat exchanger can becarried out in a cost-effective manner. In addition, the earlierapplications specify a production method for heat exchangers in which aflat-tube/fin block having free flat tube ends is provided, with theflat-tube/fin block which has free flat tube ends being soldered in asoldering furnace, with a plastic collecting tank which has receivingopenings for the flat tube ends, or a first collecting tank part withreceiving openings of said type, being placed on the free flat tube endsof the soldered flat-tube/fin block, and with an adhesive beingintroduced into a gap between the flat tube ends and the wall of thereceiving openings.

Patent Application No. DE 10 2006 055 458.2 discloses another heatexchanger having collecting tank parts which are adhesively bonded toone another. The collecting tank parts have numerous ribbed portionswhich are intended to improve the stability of the collecting tank.

It is generally known for example from DE 32 33 913 A or from DE 32 47502 A to form the collecting tank of a heat exchanger from a plasticupper part and a plastic lower part and to connect these by means ofvibration welding. The lower parts can include planar plates which haveopenings into which the ends of round tubes can be inserted, usually byexpanding the latter. There appears to be a capacity for improving theinner pressure stability of the heat exchangers, because the crosssection of the collecting tank contains very abrupt transitions.

It is the object of the invention to propose a heat exchanger which canbe produced cost-effectively and whose collecting tanks are ofparticularly pressure-stable design despite being composed of plastic.

Because the tank parts form a collecting tank cross section which isoval to round in cross section, and because the weld seam is situated ina seam preparation which is formed as a thickened portion of the wall ofat least one tank part, the pressure stability could be noticeablyincreased. The thickened portion extends as a strip preferably aroundthe edges of both walls. The seam preparation abuts against another atthe end sides of the walls and thereby preferably forms an I-shaped buttjoint.

The weld seam takes on a stepped profile in the region of the inlet oroutlet connecting pipe. In the remaining region, the weld seam runsapproximately without shoulders around the periphery of the tank parts.The profile is recessed from the first-mentioned profile of the weldseam in the region of the inlet or outlet connecting pipe, that is tosay steps are provided in the profile. The proposed embodiment likewisemakes it possible to reduce as far as possible the protrusion of thecollecting tank beyond the cooling network formed from flat tubes andfins, which contributes to a space saving.

The weld seam is a gas weld seam, which is particularly preferred, or afriction weld seam. The weld is carried out without additional material.

In addition, it is possible by means of the recessed profile of the weldseam to provide a very large flow cross section for the inlet or outletconnecting pipe. It is astonishing that it has been possible to form thecollecting tanks substantially without outer stiffening ribs even thoughthe wall thickness of the collecting tanks is comparatively low. Shouldstiffened portions be necessary for certain applications, the inventorsenvisage forming said stiffened portions on the inside of the collectingtank.

It is provided that that the cross section of the collecting tank ismore approximately round in the region of the inlet or outlet connectingpipe and merges more and more into the flat-oval cross-sectional form inthe direction of the edges of the heat exchanger. In other words, thecollecting tanks become increasingly slim toward the edges of the heatexchanger or toward the ends of the collecting tanks. Said design isparticularly space-saving and compact.

It is provided that the thickened portion contains surpluses which aredefined taking into consideration the melting of the seam, so that thefinished collecting tank constitutes a dimensionally stable product.

It is also provided that the seam preparation comprises a flange-likeprojection on the edge of one of the tank parts, which projection isarranged with a gap with respect to the edge of the other tank part,with the gap being suitable for receiving weld material, and theflange-like projection performing the function of a clean visible edge.The flange-like projection which forms the visible edge is accordinglysituated on the outside of the collecting tank. Aftertreatment of theweld seam is therefore not necessary.

The gas weld seam is a hot gas weld seam. Welding is carried out forexample using a welding device which is formed as a round orapproximately flat tube with outflow openings for the hot gas. The hotgas brings the edges of the weld seam preparation which are to be joinedup to welding temperature, that is to say the edges are thereby placedinto a pasty state. The device is thereafter removed, and the two tankparts are pressed together at the weld seam preparation and welded therewithout the aid of an additional material. Said device is anapproximately rectangular frame, since the periphery of the two tankparts has a corresponding approximately rectangular geometry. Saidoutflow openings in the tube are preferably formed on two opposite sidesof the tube, so that the hot gas can simultaneously bring both seamparts, the upper and the lower seam part, up to welding temperaturearound the entire periphery of the weld seam.

Other aspects of the invention will become apparent by consideration ofthe detailed description and accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is described in an exemplary embodiment, for which purposereference is made to the appended drawings.

FIG. 1 shows an overall view of the heat exchanger having two collectingtanks.

FIGS. 2 a and 2 b show views of the one collecting tank from FIG. 1.

FIGS. 3 a and 3 b show views of the other collecting tank from FIG. 1.

FIG. 4 shows the section A-A through a collecting tank.

FIG. 5 shows the section B-B through a collecting tank.

FIG. 6 shows the section C-C through a collecting tank.

FIG. 7 shows the section D-D through a collecting tank.

FIG. 8 shows two collecting tank parts, before being joined, with awelding device indicated in between.

FIG. 9 shows a detail of the lower collecting tank part with tube ends.

FIGS. 10-13 show perspective views of refined embodiments of a part of acollecting tank.

FIG. 14 shows an enlargement of FIG. 8.

DETAILED DESCRIPTION

Before any embodiments of the invention are explained in detail, it isto be understood that the invention is not limited in its application tothe details of construction and the arrangement of components set forthin the following description or illustrated in the following drawings.The invention is capable of other embodiments and of being practiced orof being carried out in various ways. Also, it is to be understood thatthe phraseology and terminology used herein is for the purpose ofdescription and should not be regarded as limiting. The use of“including,” “comprising,” or “having” and variations thereof herein ismeant to encompass the items listed thereafter and equivalents thereofas well as additional items. Unless specified or limited otherwise, theterms “mounted,” “connected,” “supported,” and “coupled” and variationsthereof are used broadly and encompass both direct and indirectmountings, connections, supports, and couplings. Further, “connected”and “coupled” are not restricted to physical or mechanical connectionsor couplings.

The heat exchanger shown in a front view in FIG. 1 is a liquid coolerfor motor vehicles, which has, in this case, been designed for use intrucks. The present invention could however involve other types of heatexchangers, such as, for example charge air coolers, and/or otherapplications of heat exchangers. The heat exchanger has a block of flattubes 10 and corrugated fins 2 (FIG. 9).

The flat tubes 1 and the block composed of flat tubes 10 and fins 2 canbe connected to one another in one single soldering process. The flattubes 10 and the fins 2 can be produced from one or more “endless”sheet-metal strips. The sheet metal thickness for the flat tubes 1 isapproximately in the range from 0.03-0.15 mm. The sheet metal thicknessfor the fins 2 is less than 0.10 mm. For truck applications, slightlythicker metal sheets can be used for the tubes, for example up to 0.20mm (not shown here, but present in the cited earlier applications).

The free flat tube ends 11 of the soldered block are inserted into theopenings 20 of the plastic collecting tanks 50. The walls of theopenings 20 in this exemplary embodiment have injection openings 21 inorder to be able to introduce an adhesive into the gaps 22 between theends 11 and the walls of the openings 20. It is notable that the farends 111 of the flat tubes 10 are seated tightly in the openings 20 andthat the gap 22 for the adhesive only follows thereafter. This isintended to prevent the adhesive or the adhesive connection coming intodirect contact with the cooling liquid. The fact that the far ends 111of the flat tubes 10 do not project into the interior of the collectingtanks 50 contributes noticeably to the attainment of a very low loss ofpressure (in this regard, compare also FIG. 5, in which one individualflat tube end 11 has been indicated by a dashed line). In addition, thecollecting tank part 50 b is provided between the flat tubes 10 with acorrugation which is likewise favorable for limiting the pressure loss.The details can likewise be gathered from a longitudinal section througha small piece of the lower collecting tank part 50 b as per FIG. 9. Insaid figure—as in FIG. 1—the view is of one of the narrow sides of theflat tubes 1.

However, before the adhesive bonding of the ends 11 is carried out, thecollecting tank 50 is produced from a lower collecting tank part 50 b,in which said openings 20 are provided, and an upper collecting tankpart 50 a. In the illustrated exemplary embodiment, the two parts 50 aand 50 b are connected to one another by means of a hot gas weldingprocess along a seam preparation 30. FIGS. 2 and 3 show the collectingtanks 50 in two views in each case. The two collecting tanks 50 differin said exemplary embodiment by the positioning of the inlet or outletconnecting pipe 3, 4. As also shown in FIG. 1, in the collecting tank 50arranged at the top, the inlet or outlet connecting pipe 3 is situatedin an approximately central position, and in the collecting tank 50arranged at the bottom, the inlet or outlet connecting pipe 4 isarranged more in a non-central position. The weld seam preparation 30 isalso formed accordingly. That is to say, as the figures show, the weldseam preparation 30 takes on a bent profile in the region of the inletor outlet connecting pipe 3 or 4. It is thereby possible, despite theotherwise very flat design of the collecting tank 50, to provide theinlet or outlet connecting pipe 3, 4 with a considerable flow crosssection, which brings some advantages not only in terms of the loss ofpressure. In the exemplary embodiment shown, to each side of the inletor outlet connecting pipe 3, 4 toward the ends of the collecting tanks50, the cross section becomes increasingly flat and also smaller,varying from a more round cross section (FIGS. 6, 7, 8) in the region ofthe inlet or outlet connecting pipe 3, 4 to a flat-oval cross section atthe ends, for example FIG. 4, where the horizontal axis is greater thanthe vertical axis through the oval shown.

In embodiments which are not shown, the cross section of the collectingtank 50 is for the most part approximately round as viewed over almostthe entire length. Only at the ends of the collecting tank 50 is asmaller, approximately oval cross section then provided.

In contrast to flat-oval cross sections, the invention encompasseselongate-oval cross sections which are not excluded instead of the roundcross sections. Elongate-oval cross sections are those in which thevertical axis is greater than the horizontal axis (not shown). Thesections shown in the discussed figures have been shown in FIG. 3 a. Thesections A-A to D-D which are shown are situated in each case betweentwo flat tubes 10. Said sections show the cross-sectional area of thecollecting tank 50 which becomes smaller toward the end. The crosssection of the collecting tanks 50 in a plane running through one of theflat tubes has been indicated in FIG. 5 by means of the two verticaldashed lines 12. Also shown in FIG. 5 is the protrusion 70 which is verysmall as viewed in the air flow direction (arrow), which contributes tospace saving. The slim design of the collecting tanks 50 is likewisevery space-saving and does not lead to any flow-related disadvantages.In addition, the described cross-sectional design in connection with thewelding of the tank parts 50 a, 50 b leads to extremely good pressurestability which makes it possible for the wall of the collecting tank 50to be formed without any otherwise conventional outer stiffening ribs,even though the wall thickness of the collecting tank 50 iscomparatively low. The weld seam 30 is indicated symbolically in FIG. 4.Said weld seam 30 has not been shown in the other cross sections (FIGS.5, 6, 7) but of course can be present there. As can be seen from theillustrations, the seam preparation 30 or the weld seam is situatedoutside the very short region of the inlet or outlet connecting pipe 3,4 and approximately in a central plane of the collecting tank 50. In thecase of flat-oval cross sections, the seam preparation 50 is thussituated approximately in the longer axis of the oval. Abruptcross-sectional transitions in the collecting tank 50 are largelyavoided.

FIG. 8 is now suitable for indicating how the collecting tank parts 50 aand 50 b are welded to one another. Shown in said figure is firstly thatthe weld seam preparation 30 constitutes a thickened portion of the wallof the collecting tank parts 50 a, 50 b. The weld seam preparation 30comprises a flange-like projection 31 which extends outward and alongthe seam 30. Said projection 31 is formed in the exemplary embodiment onthe upper collecting tank part 50 a, and covers the weld seam itself. Aspacing is provided between the projection 31 and the seam thickenedportion, which spacing is suitable for receiving weld material whichescapes as the tank parts 50 a, 50 b are pressed together. The weldmaterial remains hidden behind the projection 31, and there is thereforeno need to carry out weld seam aftertreatment for visual reasons. Theweld seam preparation 30 also comprises dimensional surpluses z in thethickened portion of the wall, which dimensional surpluses z serve as itwere to compensate said escaping weld material, so that the dimensionalstability of the collecting tank 50 can be ensured. In FIG. 14, saidsurpluses z, which are in the range of millimeters or less, have beenindicated on both halves of the seam preparation 30. It can also besufficient to provide surpluses z of said type only on one side, forexample only on the tank part 50 a. Also indicated in the cross sectionas per FIG. 8 is a welding device 300. Said welding device 300 is anapproximately rectangular frame composed of a tube, since the latterextends around the entire periphery of the weld seam preparation 30.Provided in the tube arc upward-pointing and downward-pointing openingsthrough which hot gas exits in order to heat the weld scam preparation30 up to welding temperature, that is to say to bring said weld seampreparation 30 into a pasty state. Once said state is reached, thewelding device 300 is removed, and the parts 50 a, 50 b are pressedtogether in a defined manner in the weld seam preparation 30 by means ofa device, thereby leading to a sealed welded connection (notillustrated).

FIGS. 10-13 show different exemplary embodiments which can inter aliayet further improve the inner pressure stability of the collecting tank50. In said embodiments, internal connections 60 have been providedwhich can be embodied as individual supports 61, 62 or else as acontinuous partition. The individual supports 61, 62 need not bearranged in a row as shown in FIG. 11, but can be provided at suitablepoints in the collecting tank 50. In FIGS. 10 and 11, a partition hasbeen arranged in the longitudinal direction, and in FIGS. 12 and 13, incontrast, in the transverse direction, of the collecting tank 50. It ishowever self-evident that longitudinal and transverse walls 60 can alsobe arranged together in one collecting tank 50. The design of thewelding device 300 has been matched to the arrangement of the internalconnection 60, since the internal connection 60 is likewise carried outby means of gas welding during the course of the production of thecollecting tank 50. Said illustrations show the above-mentioned openings301 from which the hot gas jet which impinges on the seam preparation 30exits. The reference symbols in FIG. 10 also apply to FIGS. 11-13. Theillustrations are otherwise self-explanatory.

It is possible using partitions 60 to generate advantageous throughflowcharacteristics of the heat exchanger, as have been illustrated forexample in the recently submitted German patent application with thefile reference DE 10 2006 056 774.9.

The embodiments described above and illustrated in the figures arepresented by way of example only and are not intended as a limitationupon the concepts and principles of the present invention. As such, itwill be appreciated by one having ordinary skill in the art that variouschanges in the elements and their configuration and arrangement arepossible without departing from the spirit and scope of the presentinvention as set forth in the appended claims.

1. A heat exchanger comprising: a collecting tank formed from at leasttwo collecting tank parts which are composed entirely of plastic andhave inlet or outlet connecting pipes, one of the at least twocollecting tank parts having openings for receiving tube ends, the twocollecting tank parts being welded to one another at a weld seam whichruns around a periphery of their walls; wherein the two tank parts forman oval to round collecting tank cross section between the tubes, andwherein the weld seam is situated in a seam preparation which is formedas a thickened portion of the wall of at least one tank part.
 2. Theheat exchanger according to claim 1, wherein the weld seam takes on astepped profile in the region of the inlet or outlet connecting pipe,and lies approximately in a central plane of the collecting tank in theremaining region.
 3. The heat exchanger according to claim 1, whereinthe weld seam can be carried out without a supply of additionalmaterial, and is one of a hot gas weld seam and a friction weld seam. 4.The heat exchanger according to claims 1, wherein the thickened portioncontains dimensional surpluses which replace melting weld material whenthe welding process is carried out.
 5. The heat exchanger according toclaim 1, wherein the weld seam or the seam preparation is formed as anI-shaped butt joint in the wall of the collecting tank.
 6. The heatexchanger according to claim 1, wherein the collecting tank parts areformed substantially without outer stiffening ribs.
 7. The heatexchanger according to claim 1, wherein the cross section of thecollecting tank is more approximately round or elongate-oval in theregion of the inlet or outlet connecting pipe and merges into aflat-oval cross-sectional form in the direction of edges of the heatexchanger.
 8. The heat exchanger according to claim 1, wherein thecollecting tank cross section is approximately round over most of itslength, and is of approximately oval design at opposite ends.
 9. Theheat exchanger according to claim 1, wherein that the inlet or outletconnecting pipe is an integral part of one of the collecting tank parts.10. The heat exchanger according to claim 1, wherein the seampreparation comprises a flange-like projection on an edge of one of thetank parts, wherein the projection is arranged with a gap with respectto the edge of the other tank part, with the gap being suitable forreceiving weld material, and the flange-like projection providing aclean visible edge.
 11. The heat exchanger according to claim 1,wherein, outside the region of the inlet or outlet connecting pipe, theweld seam preferably runs approximately without abrupt shoulders aroundthe periphery of the tank parts.
 12. The heat exchanger according toclaim 1, wherein the tank parts have at least one internal connection,with the internal connection having a seam preparation for a weld seam.13. The heat exchanger according to claim 12, wherein the internalconnection comprises a plurality of individual supports.
 14. The heatexchanger according to claim 12, wherein the internal connectioncomprises a media partition.
 15. The heat exchanger according to claim12, wherein the partition constitutes a longitudinal and/or transversepartition in the collecting tank.
 16. The heat exchanger according toclaim 1, wherein an extension of the tubes into the collecting tank iscomparatively small.
 17. The heat exchanger according to claim 1,wherein the tubes are flat tubes having two narrow and two wide sides,and wherein the tube ends are adhesively bonded in openings of one ofthe collecting tank parts.
 18. The heat exchanger according to claim 17,wherein the tube ends are not expanded or shaped in any other way. 19.The heat exchanger according to claim 1, wherein the flat tubes,together with corrugated fins, form a fin/tube block which is connectedby soldering and has free flat tube ends inserted into the openings ofthe collecting tank.
 20. The heat exchanger of claim 1, wherein the heatexchanger is one of a liquid cooler and a charge air cooler.